1. Field of the Invention
The present invention relates to a telescopic pivotal pipe joint, and more particularly to a telescopic pivotal pipe joint for use in a fluid transporting pipe system such as water transporting pipe system installed under the ground, the pipe joint being capable of absorbing as much as external force such as an axial compression stress or tensile stress resulting from an earthquake or differential settlement of the earth or a shearing force or bending moment in a direction transverse to the axis of the pipe, thereby precluding the possibility of breakage of weak portions of the pipe system.
2. Description of the Related Art
The conventional telescopic pivotal pipe joint is shown in FIG. 9. As shown, in this joint, a second pipe member 52 includes a semi-spherical pipe portion 52A extending with an inclination about a semi-spherical inner peripheral face of a first pipe member 51 in an invariable thickness and a straight pipe portion 52B formed integrally with one axial end of the semi-spherical pipe portion 52A. Further, on an outer peripheral face of the second pipe member 52 and at a position corresponding to the border between the semi-spherical pipe portion 52A and the straight pipe portion 52B, there is formed a first annular stopper portion 55, to which one end of a third pipe member 53 comes into contact when the second pipe member 52 and a third pipe member 53 are telescopically contracted maximally relative to each other.
On the other end of an outer peripheral face of a straight pipe portion 53B of the third pipe member 53, there is formed a semi-spherical pipe portion 53A projecting outwards in the radial direction, which is pivotally engaged and supported to a semi-spherical inner peripheral face 54a of a fourth pipe member 54. And, on the inner peripheral face of the third pipe member 53 and at a position corresponding to the border between the straight pipe portion 53B to be engaged on the straight pipe portion 52B of the second pipe member 52 and the semi-spherical pipe portion 53A, there is formed a second stopper portion 56 projecting inwards in the radial direction, to which one end of the straight pipe portion 52B of the second pipe member 52 comes into contact along the axial direction of the pipe when second pipe member 52 and the third pipe member 53 are telescopically contracted maximally relative to each other. Moreover, at one end of the straight pipe portion 52B of the second pipe member 52 and at one end of the straight pipe portion 53B of the third pipe member 53 respectively, there are formed third stopper portions 57A, 57B which come into abutment against each other along the axial direction when the second pipe member 52 and the third pipe member 53 are telescopically extended maximally relative to each other (see e.g. Japanese laid-open utility model gazette Hei. 4-66486 and Japanese laid-open utility model gazette Hei. 5-66394).
With the conventional telescopic pivotal pipe joint having the above-described construction, the maximally contracted condition of the joint is realized when the one end of the straight pipe portion 53B of the third pipe member 53 comes into abutment against the first stopper portion 55 of the second pipe member 52 and also the one end of the straight pipe portion 52B of the second pipe member 52 comes into abutment against the second stopper portion 56 of the third pipe member 53. Conversely, the maximally extended condition of the joint is realized when the third stopper portion 57A of the second pipe member 52 and the third stopper portion 57B of the third pipe member 53 come into abutment against each other. And, the respective stopper portions 55, 56, 57A, 57B are formed at the axial opposed ends of the straight pipe portion 52B of the second pipe member 52 and at the axial opposed ends of the straight pipe portion 53B of the third pipe member 53, respectively. For this reason, in order to reserve a large amount of extension/contraction between the second pipe member 52 and the third pipe member 53, it is necessary to extend the axial lengths of the respective pipe portions 52B, 53B. This invited increase in the physical size, weigh and manufacture cost of the entire pipe joint.
The present invention attends to the above-noted drawback of the prior art and a primary object of this invention is to provide an improved telescopic pivotal pipe joint which allows reservation of a greater amount of extension/contraction between the pipe members thereof when subjected to an external force without necessitating such increase of axial lengths of the pipe members.